In order to maintain the product quality of sinter magnesia (Z-Sinter), it is essential to separate the CaO coming from the raw material, as this causes the refractory products (bricks) to crack during pressing and the subsequent firing process. For this reason, the CaO content in the final product is limited with a maximum content of 2.8. The lower the content, the higher the quality of the products and thus a distinction is made between poor and rich sintered magnesia. At RHI Magnesita in Breitenau, the depletion of CaO takes place after sintering and cooling, by means of mineral processing in a sequence of crushing and screening followed by high intensity magnetic separators, which are fed with the various size fractions after screening between 0.5 mm and 8 mm. Due to the decreasing mass yield of the Z-sinter in the past years and the resulting loss of revenue, a recording of the actual state of magnetic processing is an essential first step. For this purpose, a systematic plant sampling was performed in order elaborate a reliable data set to assess the plant performance. Furthermore, tests on a laboratory magnetic separator with modified parameters were completed with the material from the sampling campaigns to clarify the potential for improvement of the magnetic separation.